Compact cameras are widely used today. And, to make these compact cameras more handy to carry, much smaller ones are desired. In various attempts to realize the further miniaturization of these compact cameras, one of the prime essentials is to reduce the space to house a photographic film.
When loaded in a compact camera, a photographic film is generally wound on a spool in roll. Therefore, to reduce the housing space for a photographic film without decreasing the number of exposures, the film itself must be made thinner. The thickness of a photographic support now in use is about 120 to 125 .mu.m and considerably thicker than that of a light-sensitive layer (20 to 30 .mu.m) formed on the support. Accordingly, thinning a photographic support is the most effective means for reducing the thickness of a whole photographic film.
As photographic supports used now, triacetylcellulose (occasionally abbreviated as TAC) films are the most typical. However, TAC films are poor in mechanical strength by nature; therefore, when made much thinner, TAC films become apt to cause troubles during conveyance or handling in a camera or in the developing process after photographing. Accordingly, it is not expedient to make the thickness of a TAC film support less than the thickness of a photographic support in use today.
On the other hand, polyethylene terephthalate films, which have so far been employed as films for X-ray photography or for photomechanical process in the photographic industry, are excellent in mechanical strength and, thereby, come to attract much attention as a photographic support which may enable the reduction of the thickness of a photographic film without lowering the mechanical strength. However, polyester resin films including polyethylene terephthalate films are unsuitable for photographic supports by nature, because these films are likely to cause a curl and can be hardly recovered from it once wound in roll.
However, the technique to provide a polyester resin with hydrophilicity disclosed in Japanese Pat. O.P.I. Pub. Nos. 120857/1990, 244446/1989, etc. has made possible to prevent polyester resin films from curl. Since then, active studies have been made with the aim of developing a thinner photographic film by use of a polyester resin support.
When such a polyester resin photographic support is used, a thinner photographic film can be certainly obtained; but, there arises a problem that the photographic film becomes apt to curl because of high water content of by a emulsion layer formed on one side of a support. To prevent such curl by balancing the moisture contents between the two sides, there is a method of using gelatin in a backing layer formed on the side of the support opposite to the emulsion layer.
A photographic film having gelatin in the backing layer does not curl, because the moisture contents of layers formed on the two sides of a photographic support are nearly equal to each other and, thereby, the curling property is balanced between the two sides. However, there arises another problem that the backing layer is stained with dust or foreign matters adsorbed thereon when brought into contact with a roller in the developing process using a cine automatic processor.